A person may have a bona fide spiritual master and may be attached to a spiritual organization, but if he is still not intelligent enough to make progress, then Kṛṣṇa from within gives him instructions so that he may ultimately come to Him without difficulty. The qualification is that a person always engage himself in Kṛṣṇa consciousness and with love and devotion render all kinds of services. He should perform some sort ofwork for Kṛṣṇa, and that work should be with love. If a devotee is not intelligent enough to make progress on the path of self-realization but is sincere and devoted to the activities of devotional service, the Lord gives him a chance to make progress and ultimately attain to Him.
(Bhagavad-Gita----10:10----purport).

No work should be done by any man except in relationship to Kṛṣṇa. This is called kṛṣṇa-karma. One may be engaged in various activities, but one should not be attached to the result of his work; the result should be done only for Him. For example, one may be engaged in business, but to transform that activity into Kṛṣṇa consciousness, one has to do business for Kṛṣṇa. If Kṛṣṇa is the proprietor of the business, then Kṛṣṇa should enjoy the profit of the business. If a businessman is in possession of thousands and thousands of dollars, and if he has to offer all this to Kṛṣṇa, he can do it. This is work for Kṛṣṇa. Instead of constructing a big building for his sense gratification, he can construct a nice temple for Kṛṣṇa, and he can install the Deity of Kṛṣṇa and arrange for the Deity's service, as is outlined in the authorized books of devotional service. This is all kṛṣṇa-karma.
(Bhagavad-Gita----11:55----purport).

No work should be done by any man except in relationship to Kṛṣṇa. This is called kṛṣṇa-karma. One may be engaged in various activities, but one should not be attached to the result of his work; the result should be done only for Him. For example, one may be engaged in business, but to transform that activity into Kṛṣṇa consciousness, one has to do business for Kṛṣṇa. If Kṛṣṇa is the proprietor of the business, then Kṛṣṇa should enjoy the profit of the business. If a businessman is in possession of thousands and thousands of dollars, and if he has to offer all this to Kṛṣṇa, he can do it. This is work for Kṛṣṇa. Instead of constructing a big building for his sense gratification, he can construct a nice temple for Kṛṣṇa, and he can install the Deity of Kṛṣṇa and arrange for the Deity's service, as is outlined in the authorized books of devotional service. This is all kṛṣṇa-karma. One should not be attached to the result of his work, but the result should be offered to Kṛṣṇa, and one should accept as prasādam the remnants of offerings to Kṛṣṇa. If one constructs a very big building for Kṛṣṇa and installs the Deity of Kṛṣṇa, one is not prohibited from living there, but it is understood that the proprietor of the building is Kṛṣṇa. That is called Kṛṣṇa consciousness. If, however, one is not able to construct a temple for Kṛṣṇa, one can engage himself in cleansing the temple of Kṛṣṇa; that is also kṛṣṇa-karma. One can cultivate a garden. Anyone who has land—in India, at least, any poor man has a certain amount of land—can utilize that for Kṛṣṇa by growing flowers to offer Him. One can sow tulasī plants, because tulasī leaves are very important and Kṛṣṇa has recommended this in Bhagavad-gītā. Patraṁ puṣpaṁ phalaṁ toyam. Kṛṣṇa desires that one offer Him either a leaf, or a flower, or fruit, or a little water—and by such an offering He is satisfied. This leaf especially refers to the tulasī. So one can sow tulasī and pour water on the plant. Thus, even the poorest man can engage in the service of Kṛṣṇa. These are some of the examples of how one can engage in working for Kṛṣṇa.
(Bhagavad-Gita----11:55----purport).

As stated before, the Supreme Lord can be appreciated only by devotional service. Therefore, one should be fully devoted. One should fix his mind fully on Kṛṣṇa in order to achieve Him. One should work only for Kṛṣṇa. It does not matter in what kind of work one engages, but that work should be done only for Kṛṣṇa. That is the standard of devotional service. The devotee does not desire any achievement other than pleasing the Supreme Personality of Godhead. His life's mission is to please Kṛṣṇa, and he can sacrifice everything for Kṛṣṇa's satisfaction, just as Arjuna did in the Battle of Kurukṣetra. The process is very simple: one can devote himself in his occupation and engage at the same time in chanting Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. Such transcendental chanting attracts the devotee to the Personality of Godhead.
(Bhagavad-Gita----12:6-7----purport).

Prescribed duties must be performed with this mentality. One should act without attachment for the result; he should be disassociated from the modes of work. A man working in Kṛṣṇa consciousness in a factory does not associate himself with the work of the factory, nor with the workers of the factory. He simply works for Kṛṣṇa. And when he gives up the result for Kṛṣṇa, he is acting transcendentally.
(Bhagavad-Gita----18:9----purport).

It is said in Bhagavad-gītā that one can never give up work at any time. Therefore he who works for Kṛṣṇa and does not enjoy the fruitive results, who offers everything to Kṛṣṇa, is actually a renouncer. There are many members of the International Society for Krishna Consciousness who work very hard in their office or in the factory or some other place, and whatever they earn they give to the Society. Such highly elevated souls are actually sannyāsīs and are situated in the renounced order of life. It is clearly outlined here how to renounce the fruits of work and for what purpose fruits should be renounced.
(Bhagavad-Gita----18:11----purport).

If one engages himself in the service of the Lord through his life, wealth, words, intelligence and everything he possesses, he will always be liberated in any condition. Such a person is called a jīvan-mukta, one who is liberated during this lifetime. Devoid of Kṛṣṇa consciousness, those who engage in material activities simply become more entangled in material bondage. They have to suffer and enjoy the actions and reactions of all activity. This Kṛṣṇa consciousness movement is therefore the greatest boon to humanity because it keeps one always engaged in Kṛṣṇa's service. The devotees think of Kṛṣṇa, act for Kṛṣṇa, eat for Kṛṣṇa, sleep for Kṛṣṇa and work for Kṛṣṇa. Thus everything is engaged in the service of Kṛṣṇa. A total life in Kṛṣṇa consciousness saves one from material contamination.
(Srimad Bhagavatam----4:30:19----purport).

The real question is how can we remain unpolluted by material contamination while in the material world. It was Rūpa Gosvāmī who explained that we can remain uncontaminated while in the world if we simply make it our ambition to serve Kṛṣṇa. One may then justifiably ask, "How can I serve?" Obviously this is not simply a matter of meditation, which is just an activity of the mind, but of practical work. Love of Kṛṣṇa's service can only be attained by working for Kṛṣṇa. In such work, we should leave no resource unused. Whatever is there, whatever we have, should be used for Kṛṣṇa. We can use everything: typewriters, automobiles, airplanes, missiles—anything. If we simply speak to people about Kṛṣṇa consciousness, we are also rendering service. If our minds, senses, speech, money and energies are thus engaged in the service of Kṛṣṇa, we cannot be considered to be existing in material nature. By virtue of spiritual consciousness, or Kṛṣṇa consciousness, we transcend the platform of material nature. It is a fact that Kṛṣṇa, His expansions and His devotees—that is, those who work for Him—are not in material nature, although people with a poor fund of knowledge think that they are.
(Teachings of Lord Caitanya).